[srlaudio]

Hey One in the Pipe, Fabric wrapped fiberglas panels are really low tech construction easily achieved by the DIY crowd.  QRD panels are a horse of a different color.  The formulas are readily available, there are variables such as target frequency and the prime number sequence which must be chosen to generate different panel designs.  The low priced diffusers you mentioned are made by making a mold and then stamping out the pattern in plastic.  It is expensive to develop the mold, but then panels can be stamped out at a reasonable cost.  The drawback to these is that they are hollow and very light in weight, so the attachment must be really good to avoid them "buzzing" against the wall or in their frame.  Another approach is to use wood or acrylic to craft a diffuser.  This is time consuming and must be done with a high degree of precision to achieve the desired results.  The approach I use is more in line with high tech manufacturing in general.  My panels are cut from solid blocks of dense material by CNC factory machines with a high degree of precision.  To use these machines all designs must be in AUTOCAD file format.  This approach gives me great flexibility to generate lots of variation in design.  I have used that to test lots of different dimension panels and have found that generally the bigger they are, the better they work.  The step of converting designs into AUTOCAD is beyond the scope of the basic DIYer.  I can't begin to explain to you how to do it if you do not already know.  One thing that isn't discussed very much is that research has shown that it is bad practice to repeat QRD's horizontally.  Their dispersion pattern is broad horizontally and tight (ie 90 degrees off the top and bottom vertically)  When you place multiples side by side, they interfere with each other and cause lobing, which is NOT what you want.  You can stack them vertically with good effect to broaden the vertical coverage.  It strikes me how similar this is to line array speaker design.  I have sort of a good answer for your bang for the buck question.  I have pondered how to make small, easy to ship and handle diffusers and have built prime 7 designs as have other manufacturers.  It made sense to me that since people were buying three at at time, that instead of making 3 of the same thing, I could make three panels that fit together like a puzzle to make a larger diffuser.  It worked!  I have three panel that make one prime 23 diffuser and am making it a package to go at $500.00!  That is sixteen square ft so the cost/sq ft is very happening, and the effect of the whole thing being one diffuser makes it perform like no other!  Here is a pic of where I demoed them at the Nashville Guitar Amp Expo.  I stacked two sets of these together to make a floor to ceiling diffuser!


These are painted gloss black with high quality enamel, it makes it hard to get a good picture, they do look good however in person.....

[Glenn Kuras]

How does your diffusion product compare, price-wise, with acoustic fiberglass panels?  Also, what opportunities are there for DIY'ers?  I have (22) 4'X8' acoustic panels in my room.  How much would 176 square feet of your diffusers cost?  No one here disagrees with diffusion.  I would like some diffusers in my room.  The problem is the cost.  Just to replace the   ( 8 ) panels on my ceiling with low/moderately-priced diffuser panels would cost $800.00 plus shipping.  The four panels on my ceiling cost less than $50.00 each to make.

As srlaudio pointed out

Fabric wrapped fiberglas panels are really low tech construction easily achieved by the DIY crowd.

Honestly diffusion is a more expensive, but you can build it as well (just like absorption). It really is about balance in the room. Use panels for bass trapping and early reflection points and diffusion beyond that. There really is not a "one size fits all" in acoustics.

[flintstone]

You don't absorb the back wave of a dipole...bad advice from experts  The dipoles need to be out "at least" 5' from the wall (at least 10 milliseconds of rear wave delay needed at your ears), and an untreated wall, or some small amount of diffusion if you must (usually when you can't get the 5' needed).

Tweeters should be on the inside (except in narrow rooms)....and none, or a very small amount of toe-in should be used (unless you must place the tweeters on the outside). You will find a huge amount of conflicting advice as you have already read here, and this is because of the band aid approach many owners use to fix setup problems caused by small room placement, of large room speakers.

Use bass traps in corners, reflection points....and so on.


Dave

[bdiament]

Hi Dave,

I would agree that one does not want to "absorb the back wave of a dipole". 
What needs absorption is not the back wave but the reflection of the back wave coming from the wall behind the speakers. 

Some folks like the coloration and sense of "added space" the reflection - or diffused reflection - appears to add.  This is not the space contained in the recording, it is an artifact of the reflection.

Just my perspective.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

[flintstone]

Hi Dave,

I would agree that one does not want to "absorb the back wave of a dipole". 
What needs absorption is not the back wave but the reflection of the back wave coming from the wall behind the speakers. 

Some folks like the coloration and sense of "added space" the reflection - or diffused reflection - appears to add.  This is not the space contained in the recording, it is an artifact of the reflection.

Just my perspective.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

Hi Barry


There is no point in buying and owning a dipole speaker if you don't want that "added space"  .....better to just buy monopoles, if thats your thing.


Dave

[srlaudio]

Hey Barry, I like your posts, I can identify, I am a studio dog as well!   lol.....
Well I subscribe to the theory that your room is part of your audio system, it definitely has a "signature" that you hear along with your mixes.  Everyone knows that if you put a stereo in a gymnasium, it sounds a little bewildering, on the other hand I don't think anybody wants to listen in an anechoic chamber.  Just sitting in one is like a vacuum on your ears!  So what to do????  A dipole speaker is not my cup of tea, I like a point source.  But if the speaker sends out an identical wavefront to the rear, how do you "get rid" of the reflection in a graceful way?  If you build a Hidley full range trap five feet deep, is that the right approach?  Or do you leave a flat sheetrock wall for them to bounce off of?  I play a trombone professionally, and I can tell you I prefer the sound of a large diffuser coming back at me as opposed to a flat sheetrock wall.....  So logically, I think the people that want the dipole sound, need to "get their money's worth" and have a pleasant, diffuse sound from their back wave.  Hey man all of this is worth 2 cents, I know...lol....

Allen Rumbaugh

[bpape]

While we do not want to absorb the backwave of a dipole, we still need to address the potential comb filtering issues that the reflections off that wave from the wall can cause.  The way to do that is through diffusion which will minimize the comb filtering without killing the wave's energy.

One can orient the ribs vertically to trick the ear into believing the soundstage is wider (especially effective in a narrow room) or we can orient them horizontally, which will scatter in the vertical dimension and can increast perceived soundstage height.

Bryan

[jtwrace]

One can orient the ribs vertically to trick the ear into believing the soundstage is wider (especially effective in a narrow room)
Bryan

Being a user of the D1's, I can say this works!   

[flintstone]

While we do not want to absorb the backwave of a dipole, we still need to address the potential comb filtering issues that the reflections off that wave from the wall can cause.  The way to do that is through diffusion which will minimize the comb filtering without killing the wave's energy.

One can orient the ribs vertically to trick the ear into believing the soundstage is wider (especially effective in a narrow room) or we can orient them horizontally, which will scatter in the vertical dimension and can increast perceived soundstage height.

Bryan

Comb filtering is not a problem if you can set them up properly...again, at least 10 ms of delay. If you get the proper amount of delay of the rear wave, the ear detects it as just any other reflection....ie, rear wall, side wall...and not part of the direct sound. The direct sound should only be the front wave.

Small room setup is a problem with dipoles, I agree with your point>

Dave

[NekoAudio]

There is no point in buying and owning a dipole speaker if you don't want that "added space"  .....better to just buy monopoles, if thats your thing.

I prefered the quickness and clarity of ribbon/planars, which is why I went with Maggies. But I also don't want the "added space". Guess I'm just uniquely using my Maggies.

I also still use a subwoofer because they can't produce the necessary bass (even "full-range" box speakers can't IMO). My sides are relatively open, so I probably don't have the same rear wave characteristics as other people.

[flintstone]

There is no point in buying and owning a dipole speaker if you don't want that "added space"  .....better to just buy monopoles, if thats your thing.

I prefered the quickness and clarity of ribbon/planars, which is why I went with Maggies. But I also don't want the "added space". Guess I'm just uniquely using my Maggies.

I also still use a subwoofer because they can't produce the necessary bass (even "full-range" box speakers can't IMO). My sides are relatively open, so I probably don't have the same rear wave characteristics as other people.

No, your not uniquely using them, most people can't set them up properly....I was once in the same boat although I don't own Maggies, (Apogee MiniGrands and Apogee Duetta Signatures). Before I built my room I had mine setup "as good as I could" in a fairly small room....whats a fellow to do  I built a 25'x 23'x 9' room around 7-8 years ago and the Apogees are on the 25' wall (they sound nothing like they did back then)....outstanding is an understatement now  I've heard nothing up to $15,000 that can hang with them.....(maybe as good?.....but not better!)


Dave

[NekoAudio]

That's a nice looking setup, Dave. I have a very large room, but of course my ideal would be no walls at all.

[bpape]

While we do not want to absorb the backwave of a dipole, we still need to address the potential comb filtering issues that the reflections off that wave from the wall can cause.  The way to do that is through diffusion which will minimize the comb filtering without killing the wave's energy.

One can orient the ribs vertically to trick the ear into believing the soundstage is wider (especially effective in a narrow room) or we can orient them horizontally, which will scatter in the vertical dimension and can increast perceived soundstage height.

Bryan

Comb filtering is not a problem if you can set them up properly...again, at least 10 ms of delay. If you get the proper amount of delay of the rear wave, the ear detects it as just any other reflection....ie, rear wall, side wall...and not part of the direct sound. The direct sound should only be the front wave.

Small room setup is a problem with dipoles, I agree with your point>

Dave

Well, as you move away, the comb filtering simply becomes lower in frequency.  It's then termed more SBIR.  You're correct that at that point the size of the waves are as long or longer than the time involved - but that doesn't change how it impacts frequency response.  Move them 6" forward or backward and you change the bottom end reinforcement/cancellation.

Bryan

[bdiament]

Hi Dave,

Hi Barry

There is no point in buying and owning a dipole speaker if you don't want that "added space"  .....better to just buy monopoles, if thats your thing.

Dave

That's one perspective and if it is what you like, I respect that.  My perspective is a bit different. 

I like the fact that dipoles tend to excite room modes only in the front to back dimension at not in the lateral or vertical dimensions.

I want any "space" I hear to come from the recording and not be artificially added by the room.  (They don't sound at all the same.)

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

[bdiament]

Hi Allen,

Hey Barry, I like your posts, I can identify, I am a studio dog as well!   lol.....
Well I subscribe to the theory that your room is part of your audio system, it definitely has a "signature" that you hear along with your mixes.  Everyone knows that if you put a stereo in a gymnasium, it sounds a little bewildering, on the other hand I don't think anybody wants to listen in an anechoic chamber.  Just sitting in one is like a vacuum on your ears!  So what to do????  A dipole speaker is not my cup of tea, I like a point source.  But if the speaker sends out an identical wavefront to the rear, how do you "get rid" of the reflection in a graceful way?  If you build a Hidley full range trap five feet deep, is that the right approach?  Or do you leave a flat sheetrock wall for them to bounce off of?  I play a trombone professionally, and I can tell you I prefer the sound of a large diffuser coming back at me as opposed to a flat sheetrock wall.....  So logically, I think the people that want the dipole sound, need to "get their money's worth" and have a pleasant, diffuse sound from their back wave.  Hey man all of this is worth 2 cents, I know...lol....

Allen Rumbaugh

I suppose it is all a matter of one's perspective and ones preference.

I should clarify my earlier statement and say it is (in my view) the early reflection of the back wave that needs absorption.

I would also say if the room's "signature" is evident, its acoustics are not properly treated.  A well designed acoustic treatment will effectively remove the room from the equation, allowing you to hear the room contained in the recording (whether it is real or artificially created).

This should not be confused with a "dead" room, which still has a signature, not to mention the discomfort such a space engenders in most listeners.

I understand that as with anything in audio, some folks will like a sound that departs from an accurate representation of what is contained in the recording.  That is a personal choice.  I know many folks who use dipoles for their numerous benefits and not as generators of artificial "space".  I believe it is mistaken (at best) to think this characteristic is an inherent quality of dipoles.  If they are properly set up, it most certainly is not.

Just my perspective.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

[bdiament]

Hi Dave,

Comb filtering is not a problem if you can set them up properly...again, at least 10 ms of delay. If you get the proper amount of delay of the rear wave, the ear detects it as just any other reflection....ie, rear wall, side wall...and not part of the direct sound. The direct sound should only be the front wave.

Small room setup is a problem with dipoles, I agree with your point>

Dave

A delay is not sufficient as it is merely a delay.  While I agree 10 ms is a good start, if left untreated, the reflection from the front wall will result in a second "attack" on transients.  This is audible and quite easily measurable.

Diffusing the delayed reflection will only smear it out in time.  I would never use diffusion for any sound so close in time to the direct signal.  Just my perspective but it is so because I hear the smear (in any room I've been in with this sort of setup).  Absorb the early reflection and the problem goes away, period.  What is left is the sound contained in the recording, un-"enhanced".
Of course, this is only a good thing if that is what one seeks to hear.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

[flintstone]

Barry

I couldn't disagree with you more, although I respect your opinion...and all others. It reads to me that you are a monopole box guy, with a dislike for dipole sound?, and you would take all dipoles, and turn them into monopoles  (although that was not the designers intent)

I understand that reflictions off of walls cause problems, but they are also the life of the music. The rear wave of a dipole is no different than any other room reflection...I take it you would absorb them all ?


I have lots of speakers, small boxes, large boxes, fullrange dipoles, hybrid dipoles. I'll take the fullrange dipoles over them all...setup in my room as stated (I would NEVER absorb the rear wave, I've done it before as a test) That said...I don't mind if someone else wants to do it?...although I would never give them that advice. I would prefer they buy a different kind of speaker (some hybrids would be better).


Dave

[bdiament]

Hi Dave,

Barry

I couldn't disagree with you more, although I respect your opinion...and all others. It reads to me that you are a monopole box guy, with a dislike for dipole sound?, and you would take all dipoles, and turn them into monopoles  (although that was not the designers intent)

I understand that reflictions off of walls cause problems, but they are also the life of the music. The rear wave of a dipole is no different than any other room reflection...I take it you would absorb them all ?


I have lots of speakers, small boxes, large boxes, fullrange dipoles, hybrid dipoles. I'll take the fullrange dipoles over them all...setup in my room as stated (I would NEVER absorb the rear wave, I've done it before as a test) That said...I don't mind if someone else wants to do it?...although I would never give them that advice. I would prefer they buy a different kind of speaker (some hybrids would be better).

Dave

I spoke of absorbing early reflections, not all reflections.

And not wanting to contaminate the information contained in a recording with arbitrary and artificially created "room" information in no way suggests monopoles.

In making recordings and in evaluating recordings I mix or master, I need to hear the recording and only the recording.  I feel the same way when listening for pleasure.

When I make a recording, I spend a lot of time in selecting the venue in which the performance will occur.  Different types of music require different spaces.  For example, a vocal chorale might sound its best in a somewhat reverberant church.  A solo classical guitar should be heard in an intimate setting.  A jazz quintet or a rock band may require a certain type of auditorium.  (I don't use studios, preferring instead to record in spaces that support the instrumentation in the context it is intended to be heard.)

I use a special stereo microphone array, utilizing a matched pair of microphones and a special baffle between them, in order to supply all of the cues Nature has supplied us with for localization of sounds.  When I'm lucky, the results give the listener the feeling they are in the room in which the performance took place.  Soundstage dimensions and image size match what I hear from the position of the microphone array at the recording session.

Adding the listening room to this equation would serve only to obscure the room that is in the recording as well as altering the soundstage dimensions and image placement.

There is nothing like attending the original recording session to get a reference for how accurate (or not) the playback is.

In the end, I suppose we must agree to disagree.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

[flintstone]

Hi Dave,

Barry

I couldn't disagree with you more, although I respect your opinion...and all others. It reads to me that you are a monopole box guy, with a dislike for dipole sound?, and you would take all dipoles, and turn them into monopoles  (although that was not the designers intent)

I understand that reflictions off of walls cause problems, but they are also the life of the music. The rear wave of a dipole is no different than any other room reflection...I take it you would absorb them all ?


I have lots of speakers, small boxes, large boxes, fullrange dipoles, hybrid dipoles. I'll take the fullrange dipoles over them all...setup in my room as stated (I would NEVER absorb the rear wave, I've done it before as a test) That said...I don't mind if someone else wants to do it?...although I would never give them that advice. I would prefer they buy a different kind of speaker (some hybrids would be better).

Dave

I spoke of absorbing early reflections, not all reflections.

And not wanting to contaminate the information contained in a recording with arbitrary and artificially created "room" information in no way suggests monopoles.

In making recordings and in evaluating recordings I mix or master, I need to hear the recording and only the recording.  I feel the same way when listening for pleasure.

When I make a recording, I spend a lot of time in selecting the venue in which the performance will occur.  Different types of music require different spaces.  For example, a vocal chorale might sound its best in a somewhat reverberant church.  A solo classical guitar should be heard in an intimate setting.  A jazz quintet or a rock band may require a certain type of auditorium.  (I don't use studios, preferring instead to record in spaces that support the instrumentation in the context it is intended to be heard.)

I use a special stereo microphone array, utilizing a matched pair of microphones and a special baffle between them, in order to supply all of the cues Nature has supplied us with for localization of sounds.  When I'm lucky, the results give the listener the feeling they are in the room in which the performance took place.  Soundstage dimensions and image size match what I hear from the position of the microphone array at the recording session.

Adding the listening room to this equation would serve only to obscure the room that is in the recording as well as altering the soundstage dimensions and image placement.

There is nothing like attending the original recording session to get a reference for how accurate (or not) the playback is.

In the end, I suppose we must agree to disagree.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

I guess we disagree most on the early reflection thing, my advice is not an "early" reflection...the excepted norm is 10 millisecond "minimum" of delay for dipole rear wave delay. Anything less will not do.....enter the band-aid advice.


Dave

[bdiament]

Hi Dave,

I guess we disagree most on the early reflection thing, my advice is not an "early" reflection...the excepted norm is 10 millisecond "minimum" of delay for dipole rear wave delay. Anything less will not do.....enter the band-aid advice.

Dave

I guess you missed the part where I agreed regarding 10 ms as a good idea (although "accepted norm", which I assume you mean rather than "excepted norm", is questionable).

I'm guessing you also missed the part where I said having a 10 ms delay with no absorption of the early reflection results in a second attack, 10 ms after the initial sound.  Perhaps you don't hear this, in which case you might be considered lucky.

"Band-aid advice"?  That's not nice Dave.
I consider a 10 millisecond delay on an untreated reflection from a live wall quite audible and quite distracting.  Perhaps you don't hear this.  That's okay.  Just enjoy your music. 

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com